Characterization of Platelet Function in Patients with Bleeding Disorders: In FY2008 (the first year of this project) we have studied several patients with suspected or documented disorders of platelet function and have identified patients with deficiency of dense granules (storage pool disease), and characterized platelet function and protein content in siblings with known platelet dysfunction (White platelet syndrome), and platelet von Willebrand factor deficiency. Further, we have continued characterization of platelet function and granule protein content in a patient with excessive platelet urokinase and deficient of platelet von Willebrand factor. As we initiate these studies we have begun to define reference ranges for platelet-derived growth factor, beta-thromboglobulin, and platelet von Willebrand factor in platelet lysates. Future work will focus on measurements of other platelet proteins (e.g., fibrinogen and factor V) so as to have a panel of platelet alpha granule proteins to assess and correlate with bleeding phenotype in congenital or acquired disorders of platelet function. The ability to make a reliable, detailed characterization of platelet function may help investigators who are studying genetics of inherited platelet disorders. [unreadable] [unreadable] Characterization of D-Dimer and Related Coagulation Proteins in HIV-Infected Research Subjects Undergoing IL-2 Therapy: During the first year of this project, in support of intramural NIH research protocols, we have measured D-dimer levels on archived plasma samples from HIV-infected research subjects on anti-retroviral intervention with interleukin 2 (IL-2). We observed that D-dimer levels increased with IL-2 therapy, positively correlating with increases in C-reactive protein levels and greater pre-IL-2 HIV viremia. In HIV-infected patients with osteonecrosis, D-dimer levels were higher at the time of diagnosis than for HIV-infected patients without osteonecrosis (but not at other time points). Future work will focus on defining other coagulation parameters to determine the mechanism by which D-dimer levels are elevated in these patients.[unreadable] [unreadable] Markers of Endothelial Cell Injury and Thrombosis in Patients Undergoing Cancer Chemotherapy. During the first year of this project, in support of intramural NIH research protocols, we measured von Willebrand factor-cleaving protease levels (ADAMTS-13) and thrombomodulin in patients with hairy cell leukemia (HCL) or chronic lymphocytic leukemia (CLL) that were treated with an investigational monoclonal antibody conjugated to Pseudomonas exotoxin (BL-22). A small proportion of these patients exhibit a self-limited thrombotic, microangiopathic hemolytic anemia (TMA) after treatment. In the patients with TMA, there was no apparent correlation with ADAMTS-13 levels, however, thrombomodulin levels were elevated. This finding suggests that in some patients with TMA complicating treatment, endothelial damage may be a critical factor. In the future we will seek to characterize the nature of the endothelial damage by assessment of related endothelial markers and also to look for other signs of abnormal hemostasis in treated patients with TMA.